/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package com.feilong.lib.compress.archivers.zip;

import java.util.zip.ZipException;

/**
 * If this extra field is added as the very first extra field of the
 * archive, Solaris will consider it an executable jar file.
 * 
 * @Immutable
 */
public final class JarMarker implements ZipExtraField{

    private static final ZipShort  ID       = new ZipShort(0xCAFE);

    private static final ZipShort  NULL     = new ZipShort(0);

    private static final byte[]    NO_BYTES = new byte[0];

    private static final JarMarker DEFAULT  = new JarMarker();

    /** No-arg constructor */
    public JarMarker(){
        // empty
    }

    /**
     * Since JarMarker is stateless we can always use the same instance.
     * 
     * @return the DEFAULT jarmaker.
     */
    public static JarMarker getInstance(){
        return DEFAULT;
    }

    /**
     * The Header-ID.
     * 
     * @return the header id
     */
    @Override
    public ZipShort getHeaderId(){
        return ID;
    }

    /**
     * Length of the extra field in the local file data - without
     * Header-ID or length specifier.
     * 
     * @return 0
     */
    @Override
    public ZipShort getLocalFileDataLength(){
        return NULL;
    }

    /**
     * Length of the extra field in the central directory - without
     * Header-ID or length specifier.
     * 
     * @return 0
     */
    @Override
    public ZipShort getCentralDirectoryLength(){
        return NULL;
    }

    /**
     * The actual data to put into local file data - without Header-ID
     * or length specifier.
     * 
     * @return the data
     */
    @Override
    public byte[] getLocalFileDataData(){
        return NO_BYTES;
    }

    /**
     * The actual data to put central directory - without Header-ID or
     * length specifier.
     * 
     * @return the data
     */
    @Override
    public byte[] getCentralDirectoryData(){
        return NO_BYTES;
    }

    /**
     * Populate data from this array as if it was in local file data.
     * 
     * @param data
     *            an array of bytes
     * @param offset
     *            the start offset
     * @param length
     *            the number of bytes in the array from offset
     *
     * @throws ZipException
     *             on error
     */
    @Override
    public void parseFromLocalFileData(final byte[] data,final int offset,final int length) throws ZipException{
        if (length != 0){
            throw new ZipException("JarMarker doesn't expect any data");
        }
    }

    /**
     * Doesn't do anything special since this class always uses the
     * same data in central directory and local file data.
     */
    @Override
    public void parseFromCentralDirectoryData(final byte[] buffer,final int offset,final int length) throws ZipException{
        parseFromLocalFileData(buffer, offset, length);
    }
}
